Binder compositions comprising lignin derivatives

ABSTRACT

The present disclosure provides an adhesive composition comprising derivatives of native lignin and an isocyanate-based binder such as methylene diphenyl diisocyanate. The present compositions may further comprise formaldehyde-based resins such as PF, UF, and MF. While not wishing to be bound by theory, it is believed that incorporating derivatives of native lignin in isocyanate compositions will reduce incidence of pre-curing.

This application is a continuation of PCT/CA2011/000182, filed Feb. 15,2011; which claims the priority of U.S. Provisional Application No.61/304,745, filed Feb. 15, 2010; U.S. Provisional Application No.61/304,742, filed Feb. 15, 2010; and PCT/CA2010/000800, filed May 27,2010. The contents of the above-identified applications are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

This disclosure relates to derivatives of native lignin recovered fromlignocellulosic feedstocks, and industrial applications thereof. Moreparticularly, this disclosure relates to compositions, uses, processesand methods utilizing derivatives of native lignin.

BACKGROUND

Native lignin is a naturally occurring amorphous complex cross-linkedorganic macromolecule that comprises an integral component of all plantbiomass. The chemical structure of lignin is irregular in the sense thatdifferent structural units (e.g., phenylpropane units) are not linked toeach other in any systematic order. It is known that native lignincomprises pluralities of two monolignol monomers that are methoxylatedto various degrees (trans-coniferyl alcohol and trans-sinapyl alcohol)and a third non-methoxylated monolignol (trans-p-coumaryl alcohol).Various combinations of these monolignols comprise three building blocksof phenylpropanoid structures i.e. guaiacyl monolignol, syringylmonolignol and p-hydroxyphenyl monolignol, respectively, that arepolymerized via specific linkages to form the native ligninmacromolecule.

Extracting native lignin from lignocellulosic biomass during pulpinggenerally results in lignin fragmentation into numerous mixtures ofirregular components. Furthermore, the lignin fragments may react withany chemicals employed in the pulping process. Consequently, thegenerated lignin fractions can be referred to as lignin derivativesand/or technical lignins. As it is difficult to elucidate andcharacterize such complex mixture of molecules, lignin derivatives areusually described in terms of the lignocellulosic plant material used,and the methods by which they are generated and recovered fromlignocellulosic plant material, i.e. hardwood lignins, softwood lignins,and annual fibre lignins.

Native lignins are partially depolymerized during the pulping processesinto lignin fragments which are soluble in the pulping liquors andsubsequently separated from the cellulosic pulps. Post-pulping liquorscontaining lignin and polysaccharide fragments, and other extractives,are commonly referred to as “black liquors” or “spent liquors”,depending on the pulping process. Such liquors are generally considereda by-product, and it is common practice to combust them to recover someenergy value in addition to recovering the cooking chemicals. However,it is also possible to precipitate and/or recover lignin derivativesfrom these liquors. Each type of pulping process used to separatecellulosic pulps from other lignocellulosic components produces ligninderivatives that are very different in their physico-chemical,biochemical, and structural properties.

Given that lignin derivatives are available from renewable biomasssources there is an interest in using these derivatives in certainindustrial processes. For example, U.S. Pat. No. 5,173,527 proposesusing lignin-cellulosic materials in phenol-formaldehyde resins. A.Gregorova et al.

propose using lignin in polypropylene for it radical scavengingproperties (A. Gregorova et al., Radical scavenging capacity of ligninand its effect on processing stabilization of virgin and recycledpolypropylene, Journal of Applied Polymer Science 106-3 (2007) pp.1626-1631).

However, large-scale commercial application of the extracted ligninderivatives, particularly those isolated in traditional pulpingprocesses employed in the manufacture of pulp and paper, has beenlimited due to, for example, the inconsistency of their chemical andfunctional properties. This inconsistency may, for example, be due tochanges in feedstock supplies and the particularextraction/generation/recovery conditions. These issues are furthercomplicated by the complexity of the molecular structures of ligninderivatives produced by the various extraction methods and thedifficulty in performing reliable routine analyses of the structuralconformity and integrity of recovered lignin derivatives. Neverthelessefforts continue to use lignin derivatives on a commercial scale.

For many years fibreboard products have been manufactured from wood oragricultural substrates using various adhesives. Formaldehyde-basedresins such as phenol formaldehyde (PF), urea formaldehyde (UF) andmelamine formaldehyde (MF) are extremely common and used for a varietyof purposes such as manufacturing of housing and furniture panels suchas medium density fibreboard (MDF), oriented strand board (OSB),plywood, and particleboard. Concerns about the toxicity of formaldehydehave led regulatory authorities to mandate the reduction of formaldehydeemissions (e.g. California Environmental Protection Agency AirborneToxic Control Measure (ATCM) to Reduce Formaldehyde Emissions fromComposite Wood Products, Apr. 26, 2007). There have been attempts to addlignin derivatives to formaldehyde-based resins. However, such attemptshave not been entirely successful. For example, past attempts at addingAlcell® lignin to PF resins have been largely unsuccessful due to therelatively poor performance characteristics of the final product wherethe normalized Alcell® lignin-PF resin bond strength at 150° C. was3,079 MPa*cm²/g as tested by the ABES method (Wescott, J. M., Birkeland,M. J., Traska, A. E., New Method for Rapid Testing of Bond Strength forWood Adhesives, Heartland Resource Technologies Waunakee, Wis., U.S.A.and Frihart, C. R. and Dally, B. N., USDA Forest Service, ForestProducts Laboratory, Madison, Wis., U.S.A., Proceedings 30^(th) AnnualMeeting of The Adhesion Society, Inc., Feb. 18-21, 2007, Tampa Bay,Fla., USA). These values are significantly lower than the currentcommercial adhesives. For instance, plywood or OSB made with PF resinsare expected to have a bond strength in the region of 3,200-3,600MPa*cm²/g. Furthermore, lignin-containing PF-resins often do not curequickly enough or completely enough under normal production conditionsfor fibreboard. This lack of cure-speed and lack of bond strength haslimited the amount of lignin derivative that has been included in theformaldehyde-resins to relatively low levels.

An adhesive should meet certain criteria in order to be acceptable forindustrial use. For example, the adhesive will preferably be availablein a stable form such as a spray-dried powder or stable liquid. Theadhesive will preferably set quickly enough to enable its use as a coreadhesive for thick multi-layer panels but should not suffer fromexcessive “pre-cure”.

Methylene diphenyl diisocyanate (MDI) is a widely used diisocyanatecommonly used in the manufacture of polyurethanes and as an adhesive.MDI has the advantage that it is highly reactive and has strongbondability as well as being formaldehyde free. MDI polymerizes in thepresence of water which reduce the ecological risks associated with itsuse.

It is known to use isocyanate-based binders such as MDI for fibreboard(see, for example, U.S. Pat. No. 6,692,670) but they have not, to date,been widely adopted for various reasons such as cost, cure-rate, and theneed for release-agents to avoid the board sticking to the press-plates.

A significant issue with the use of MDI is its high sensitivity tomoisture and temperature. In many manufacturing processes MDI suffersfrom significant premature polymerization (pre-cure) leading tosubstantial loss of resin efficiency and, hence, higher resinconsumption. It is estimated that as much as 10% of the MDI may be lostto pre-curing leading to increased costs and decreased processefficiency.

SUMMARY

The present disclosure provides an adhesive composition comprisingderivatives of native lignin and an isocyanate-based binder such asmethylene diphenyl diisocyanate. The present compositions may furthercomprise formaldehyde-based resins such as PF, UF, and MF. While notwishing to be bound by theory, it is believed that incorporatingderivatives of native lignin in isocyanate compositions will reduceincidence of pre-curing.

As used herein, the terms “methylene diphenyl diisocyanate” and “MDI”encompass oligomers of methylene diphenyl diisocyanate sometimesreferred to as “pMDI” or “polymethylene polyphenylene polyisocyanate”

As used herein, the term “native lignin” refers to lignin in its naturalstate, in plant material.

As used herein, the terms “lignin derivatives” and “derivatives ofnative lignin” refer to lignin material extracted from lignocellulosicbiomass. Usually, such material will be a mixture of chemical compoundsthat are generated during the extraction process.

This summary does not necessarily describe all features of theinvention. Other aspects, features and advantages of the invention willbe apparent to those of ordinary skill in the art upon review of thefollowing description of specific embodiments of the invention.

DETAILED DESCRIPTION

The present disclosure provides compositions comprising isocyanate-basedbinder such as methylene diphenyl diisocyanate (MDI) and derivatives ofnative lignin. MDI compositions comprising lignin derivatives sufferfrom a lower incidence of pre-cure. While not wishing to be bound bytheory, lignin derivatives may reduce the sensitivity of MDI to moistureand temperature, the latter being factors responsible for early MDIpolymerization (“precure”). The incorporation of lignin in MDI can beproblematic due to the instability and irregularity of the resultinglignin-containing MDI resins. The present compositions may compriseformaldehyde-based resins comprising lignin derivatives such aslignin-phenol formaldehyde (LPF). It is believed that the presence ofisocyanate-based binder improves the cure-speed of the LPF making itmore suitable for industrial applications such as an adhesive for thecore of a multi-layer fibreboard. It is further believed that thepresence of isocyanate-based binder allows increased amounts of theformaldehyde-based resin to be substituted with lignin derivative. Forexample, the present compositions may comprise 30% or more, 35% or more,40% or more, by weight of lignin derivative.

Any suitable isocyanate-based binder. For example, polymeric MDI(polymethylene polyphenylene polyisocyanate) such as emulsifiable,polymeric MDI' s may be used. Examples of commercially availablepolymeric MDI include I-Bond® and Rubinate® such as Rubinate 1840isocyanate, Rubinate M isocyanate, Rubinate 1780 isocyante, availablefrom Huntsman Polyurethanes located in West Deptford, N.J. The MDIpreferably has a diisocyanate content of about 50% or less, about 48% orless, about 45% or less, about 40% or less, by weight.

The polymeric MDI may also contain urethane modifications, isocyanuratemodifications, biurets, ureas, etc. The polymeric MDI may be modified tobe water dispersible, and applied in an aqueous emulsion form. Such amethod for modifying the polymeric MDI to be water dispersible is fullydisclosed in the above-identified U.S. Pat. No. 3,996,154.

The polymeric MDI may be used alone, or in conjunction with other bindermaterials, including, but not limited to, formaldehyde containing bindermaterials, diluents, extenders, fillers, etc. Suitable extendersinclude, for example, oils, such as soy oil and linseed oil, solvents,lignin, carbohydrates, etc. Suitable fillers include, for example,fibreglass, plastics, waste materials, etc. Moreover, the polymeric MDImay also include fire retardants, such as, for example, ammoniumpolyphosphates, trichloropropyl phosphate (TCPP), melamine, triphenylphosphate, etc. Furthermore, the polymeric MDI may also include suitablerelease agents, such as, for example, soaps, fatty acids, waxes,silicones, fatty acid salts, etc.

Additionally, the polymeric MDI may also include biocides, such as boricacid, etc.

The present disclosure provides derivatives of native lignin recoveredduring or after pulping of lignocellulosic feedstocks. The pulp may befrom any suitable lignocellulosic feedstock including hardwoods,softwoods, annual fibres, and combinations thereof. Hardwood feedstocksinclude Acacia; Afzelia; Synsepalum duloificum; Albizia; Alder (e.g.Alnus glutinosa, Alnus rubra); Applewood; Arbutus; Ash (e.g. F. nigra,F. quadrangulata, F. excelsior, F. pennsylvanica lanceolata, F.latifolia, F. profunda, F. americana); Aspen (e.g. P. grandidentata, P.tremula, P. tremuloides); Australian Red Cedar (Toona ciliata); Ayna(Distemonanthus benthamianus); Balsa (Ochroma pyramidale); Basswood(e.g. T. americana, T. heterophylla); Beech (e.g. F. sylvatica, F.grandifolia); Birch; (e.g. Betula populifolia, B. nigra, B. papyrifera,B. lenta, B. alleghaniensis/B. lutea, B. pendula, B. pubescens);Blackbean; Blackwood; Bocote; Boxelder; Boxwood; Brazilwood; Bubinga;Buckeye (e.g. Aesculus hippocastanum, Aesculus glabra, Aesculusflava/Aesculus octandra); Butternut; Catalpa; Cherry (e.g. Prunusserotina, Prunus pennsylvanica, Prunus avium); Crabwood; Chestnut;Coachwood; Cocobolo; Corkwood; Cottonwood (e.g. nPopulus balsamifera,Populus deltoides, Populus sargentii, Populus heterophylla);Cucumbertree; Dogwood (e.g. Cornus florida, Cornus nuttallii); Ebony(e.g. Diospyros kurzii, Diospyros melanida, Diospyros crassiflora); Elm(e.g. Ulmus americana, Ulmus procera, Ulmus thomasii, Ulmus rubra, Ulmusglabra); Eucalyptus; Greenheart; Grenadilla; Gum (e.g. Nyssa sylvatica,Eucalyptus globulus, Liquidambar styraciflua, Nyssa aquatica); Hickory(e.g. Carya alba, Carya glabra, Carya ovata, Carya laciniosa); Hornbeam;Hophornbeam; Ipe; Iroko; Ironwood (e.g. Bangkirai, Carpinus caroliniana,Casuarina equisetifolia, Choricbangarpia subargentea, Copaifera spp.,Eusideroxylon zwageri, Guajacum officinale, Guajacum sanctum, Hopeaodorata, Ipe, Krugiodendron ferreum, Lyonothamnus lyonii (L.floribundus), Mesua ferrea, Olea spp., Olneya tesota, Ostrya virginiana,Parrotia persica, Tabebuia serratifolia); Jacarandá; Jotoba; Lacewood;Laurel; Limba; Lignum vitae; Locust (e.g. Robinia pseudacacia, Gleditsiatriacanthos); Mahogany; Maple (e.g. Acer saccharum, Acer nigrum, Acernegundo, Acer rubrum, Acer saccharinum, Acer pseudoplatanus); Meranti;Mpingo; Oak (e.g. Quercus macrocarpa, Quercus alba, Quercus stellata,Quercus bicolor, Quercus virginiana, Quercus michauxii, Quercus prinus,Quercus muhlenbergii, Quercus chrysolepis, Quercus lyrata, Quercusrobur, Quercus petraea, Quercus rubra, Quercus velutina, Quercuslaurifolia, Quercus falcata, Quercus nigra, Quercus phellos, Quercustexana); Obeche; Okoumé; Oregon Myrtle; California Bay Laurel; Pear;Poplar (e.g. P. balsamifera, P. nigra, Hybrid Poplar(Populus×canadensis)); Ramin; Red cedar; Rosewood; Sal; Sandalwood;Sassafras; Satinwood; Silky Oak; Silver Wattle; Snakewood; Sourwood;Spanish cedar; American sycamore; Teak; Walnut (e.g. Juglans nigra,Juglans regia); Willow (e.g. Salix nigra, Salix alba); Yellow poplar(Liriodendron tulipifera); Bamboo; Palmwood; and combinations/hybridsthereof.

For example, hardwood feedstocks for the present disclosure may beselected from Acacia, Aspen, Beech, Eucalyptus, Maple, Birch, Gum, Oak,Poplar, and combinations/hybrids thereof. The hardwood feedstocks forthe present disclosure may be selected from Populus spp. (e.g. Populustremuloides), Eucalyptus spp. (e.g. Eucalyptus globulus), Acacia spp.(e.g. Acacia dealbata), and combinations/hybrids thereof.

Softwood feedstocks include Araucaria (e.g. A. cunninghamii, A.angustifolia, A. araucana); softwood Cedar (e.g. Juniperus virginiana,Thuja plicata, Thuja occidentalis, Chamaecyparis thyoides Callitropsisnootkatensis); Cypress (e.g. Chamaecyparis, Cupressus Taxodium,Cupressus arizonica, Taxodium distichum, Chamaecyparis obtusa,Chamaecyparis lawsoniana, Cupressus semperviren); Rocky Mountain Douglasfir; European Yew; Fir (e.g. Abies balsamea, Abies alba, Abies procera,Abies amabilis); Hemlock (e.g. Tsuga canadensis, Tsuga mertensiana,Tsuga heterophylla); Kauri; Kaya; Larch (e.g. Larix decidua, Larixkaempferi, Larix laricina, Larix occidentalis); Pine (e.g. Pinus nigra,Pinus banksiana, Pinus contorta, Pinus radiata, Pinus ponderosa, Pinusresinosa, Pinus sylvestris, Pinus strobus, Pinus monticola, Pinuslambertiana, Pinus taeda, Pinus palustris, Pinus rigida, Pinusechinata); Redwood; Rimu; Spruce (e.g. Picea abies, Picea mariana, Picearubens, Picea sitchensis, Picea glauca); Sugi; and combinations/hybridsthereof.

For example, softwood feedstocks which may be used herein include cedar;fir; pine; spruce; and combinations thereof. The softwood feedstocks forthe present disclosure may be selected from loblolly pine (Pinus taeda),radiata pine, jack pine, spruce (e.g., white, interior, black), Douglasfir, Pinus silvestris, Picea abies, and combinations/hybrids thereof.The softwood feedstocks for the present disclosure may be selected frompine (e.g. Pinus radiata, Pinus taeda); spruce; and combinations/hybridsthereof.

Annual fibre feedstocks include biomass derived from annual plants,plants which complete their growth in one growing season and thereforemust be planted yearly. Examples of annual fibres include: flax, cerealstraw (wheat, barley, oats), sugarcane bagasse, rice straw, corn stover,hemp, fruit pulp, alfa grass, switchgrass, and combinations/hybridsthereof. Industrial residues like corn cobs, fruit peals, seeds, etc.may also be considered annual fibres since they are commonly derivedfrom annual fibre biomass such as edible crops and fruits. For example,the annual fibre feedstock may be selected from wheat straw, cornstover, corn cobs, sugar cane bagasse, and combinations/hybrids thereof.

The derivatives of native lignin will vary with the type of process usedto separate native lignins from cellulose and other biomassconstituents. Preparations very similar to native lignin can be obtainedby (1) solvent extraction of finely ground wood (milled-wood lignin,MWL) or by (2) acidic dioxane extraction (acidolysis) of wood.Derivatives of native lignin can be also isolated from biomasspre-treated using (3) steam explosion, (4) dilute acid hydrolysis, (5)ammonia fibre expansion, (6) autohydrolysis methods. Derivatives ofnative lignin can be recovered after pulping of lignocellulosicsincluding industrially operated (3) kraft and (4) soda pulping (andtheir modifications) and (5) sulphite pulping. In addition, a number ofvarious pulping methods have been developed but not industriallyintroduced. Among them four major “organosolv” pulping methods tend toproduce highly-purified lignin mixtures. The first organosolv methoduses ethanol/solvent pulping (aka the Alcell® process); the secondorganosolv method uses alkaline sulphite anthraquinone methanol pulping(aka the “ASAM” process); the third organosolv process uses methanolpulping followed by methanol, NaOH, and anthraquinone pulping (aka the“Organocell” process); the fourth organosolv process uses aceticacid/hydrochloric acid or formic acid pulping (aka the “Acetosolv”process).

It should be noted that kraft pulping, sulphite pulping, and ASAMorganosolv pulping will generate derivatives of native lignin containingsignificant amounts of organically-bound sulphur which may make themunsuitable for certain uses. Acid hydrolysis, soda pulping, steamexplosion, Alcell® pulping, Organocell pulping, and Acetosolv pulpingwill generate derivatives of native lignin that are sulphur-free orcontain low amounts of inorganic sulphur.

Organosolv processes, particularly the Alcell® process, tend to be lessaggressive and can be used to separate highly purified ligninderivatives and other useful materials from biomass without excessivelyaltering or damaging the native lignin building blocks. Such processescan therefore be used to maximize the value from all the componentsmaking up the biomass. Organosolv extraction processes however typicallyinvolve extraction at higher temperatures and pressures with a flammablesolvent compared to other industrial processes and thus are generallyconsidered to be more complex and expensive.

A description of the Alcell® process can be found in U.S. Pat. No.4,764,596 (herein incorporated by reference). The process generallycomprises pulping or pre-treating a fibrous biomass feedstock withprimarily an ethanol/water solvent solution under conditions thatinclude: (a) 60% ethanol/40% water, (b) temperature of about 180° C. toabout 210° C., (c) pressure of about 20 atm to about 35 atm, and (d) aprocessing time of 5-120 minutes.

Derivatives of native lignin are fractionated from the native ligninsinto the pulping liquor which also receives solubilised hemicelluloses,other carbohydrates and other extractives such as resins, organic acids,phenols, and tannins. Organosolv pulping liquors comprising thefractionated derivatives of native lignin and other extractives from thefibrous biomass feedstocks, are often called “black liquors”. Theorganic acid and extractives released by organosolv pulpingsignificantly acidify the black liquors to pH levels of about 5 andlower. After separation from the cellulosic pulps produced during thepulping process, the derivatives of native lignin are recovered from theblack liquors by depressurization followed by flashing with cold waterwhich will cause the fractionated derivatives of native lignin toprecipitate thereby enabling their recovery by standard solids/liquidsseparation processes. Various disclosures exemplified by U.S. Pat. No.7,465,791 and PCT Patent Application Publication No. WO 2007/129921,describe modifications to the Alcell organosolv process for the purposesof increasing the yields of fractionated derivatives of native ligninrecovered from fibrous biomass feedstocks during biorefining.Modifications to the Alcell organosolv process conditions includedadjusting: (a) ethanol concentration in the pulping liquor to a valueselected from a range of 35%-85% (w/w) ethanol, (b) temperature to avalue selected from a range of 100° C. to 350° C., (c) pressure to avalue selected from a range of 5 atm to 35 atm, and (d) processing timeto a duration from a range of 20 minutes to about 2 hours or longer, (e)liquor-to-wood ratio of 3:1 to 15:1 or higher, (f) pH of the cookingliquor from a range of 1 to 6.5 or higher if a basic catalyst is used.

The derivatives of native lignin herein may be obtained by:

-   -   (a) pulping a fibrous biomass feedstock with an organic        solvent/water solution,    -   (b) separating the cellulosic pulps or pre-treated substrates        from the pulping liquor or pre-treatment solution,    -   (c) recovering derivatives of native lignin.

The organic solvent may be selected from short chain primary andsecondary alcohols, such as such as methanol, ethanol, propanol, andcombinations thereof. For example, the solvent may be ethanol. Theliquor solution may comprise about 20%, by weight, or greater, about 30%or greater, about 50% or greater, about 60% or greater, about 70% orgreater, of ethanol.

Step (a) of the process may be carried out at a temperature of fromabout 100° C. and greater, or about 120° C. and greater, or about 140°C. and greater, or about 160° C. and greater, or about 170° C. andgreater, or about 180° C. and greater. The process may be carried out ata temperature of from about 300° C. and less, or about 280° C. and less,or about 260° C. and less, or about 240° C. and less, or about 220° C.and less, or about 210° C. and less, or about 205° C. and less, or about200° C. and less.

Step (a) of the process may be carried out at a pressure of about 5 atmand greater, or about 10 atm and greater, or about 15 atm and greater,or about 20 atm and greater, or about 25 atm and greater, or about 30atm and greater. The process may be carried out at a pressure of about150 atm and less, or about 125 atm and less, or about 115 atm and less,or about 100 atm and less, or about 90 atm and less, or about 80 atm andless.

The fibrous biomass may be treated with the solvent solution of step (a)for about 1 minute or more, about 5 minutes or more, about 10 minutes ormore, about 15 minutes or more, about 30 minutes or more. The fibrousbiomass may be treated with the solvent solution of step (a) at itsoperating temperature for about 360 minutes or less, about 300 minutesor less, about 240 minutes or less, about 180 minutes or less, about 120minutes or less.

The pH of the pulp liquor may, for example, be from about 1 to about 6,or from about 1.5 to about 5.5.

The weight ratio of liquor to biomass may be any suitable ratio. Forexample, from about 4 or 5:1 to about 15:1, from about 5.5:1 to about10:1; from about 6:1 to about 8:1.

The lignin derivatives herein may, for example, have an aliphatichydroxyl content of from about 0.1 mmol/g to about 8 mmol/g; about 0.4mmol/g to about 7 mmol/g; about 0.6 mmol/g to about 6.5 mmol/g; about0.8 mmol/g to about 6 mmol/g.

The term “aliphatic hydroxyl content” refers to the quantity ofaliphatic hydroxyl groups in the lignin derivatives and is thearithmetic sum of the quantity of primary and secondary hydroxyl groups(OHal=OHpr+OHsec). The aliphatic hydroxyl content can be measured byquantitative ¹³C high resolution NMR spectroscopy of acetylated andnon-acetylated lignin derivatives, using, for instance, 1,3,5-trioxaneand tetramethyl silane (TMS) as internal reference. For the dataanalysis “BASEOPT” (DIGMOD set to baseopt) routine in the softwarepackage TopSpin 2.1.4 was used to predict the first FID data point backat the mid-point of ¹³C r.f. pulse in the digitally filtered data wasused. For the NMR spectra recording a Bruker AVANCE II digital NMRspectrometer running TopSpin 2.1 was used. The spectrometer used aBruker 54 mm bore Ultrashield magnet operating at 14.1 Tesla (600.13 MHzfor ¹H, 150.90 MHz for ¹³C). The spectrometer was coupled with a BrukerQNP cryoprobe (5 mm NMR samples, ¹³C direct observe on inner coil, ¹Houter coil) that had both coils cooled by helium gas to 20K and allpreamplifiers cooled to 77K for maximum sensitivity. Sample temperaturewas maintained at 300 K±0.1 K using a Bruker BVT 3000 temperature unitand a Bruker BCU05 cooler with ca. 95% nitrogen gas flowing over thesample tube at a rate of 800 L/h.

The present lignin derivatives may have any suitable phenolic hydroxylcontent such as from about 2 mmol/g to about 8 mmol/g. For example, thephenolic hydroxyl content may be from about 2.5 mmol/g to about 7mmol/g; about 3 mmol/g to about 6 mmol/g.

The present lignin derivatives may have any suitable number averagemolecular weight (Mn). For example, the Mn may be from about 200 g/molto about 3000 g/mol; about 350 g/mol to about 2000 g/mol; about 500g/mol to about 1500 g/mol.

The present lignin derivatives may have any suitable weight averagemolecular weight (Mw). For example, the Mw may be from about 500 g/molto about 5000 g/mol; about 750 g/mol to about 4000 g/mol; about 900g/mol to about 3500 g/mol.

The present lignin derivatives may have any suitable polydispersity (D).For example, the D may be from about 1 to about 5; from about 1.2 toabout 4; from about 1.3 to about 3.5; from about 1.4 to about 3.

The present lignin derivatives are preferably hydrophobic.Hydrophobicity may be assessed using contact angle measurements.

The present lignin derivatives may comprise alkoxy groups. For example,the present lignin derivatives may have an alkoxy content of 2 mmol/g orless; about 1.4 mmol/g or less; about 1.2 mmol/g or less; about 1 mmol/gor less; about 0.8 mmol/g or less; about 0.7 mmol/g or less; about 0.6mmol/g or less; about 0.5 mmol/g or less; about 0.4 mmol/g or less;about 0.3 mmol/g or less. The present lignin derivatives may have analkoxy content of 0.001 mmol/g or greater, about 0.01 mmol/g of greater,about 0.05 mmol/g or greater, about 0.1 mmol/g or greater.

The present lignin derivatives may comprise ethoxy groups. It has beenfound that derivatives of native lignin having an ethoxy content of 0.45mmol/g or greater result in PF-resins having acceptable bond-strengths.For example, about 0.5 mmol/g or greater; about 0.6 mmol/g or greater;about 0.7 mmol/g or greater; about 0.8 mmol/g or greater; about 0.9mmol/g or greater; about 1 mmol/g or greater; about 1.1 mmol/g orgreater; about 1.2 mmol/g or greater. The present lignin derivativesmay, for example, have an ethoxy content of about 3.75 mmol/g or less;3.5 mmol/g or less; 3.25 mmol/g or less; 3 mmol/g or less; 2.75 mmol/gor less; 2.5 mmol/g or less; 2.25 mmol/g or less; 2 mmol/g or less; 1.9mmol/g or less; 1.8 mmol/g or less; 1.7 mmol/g or less; 1.6 mmol/g orless; 1.5 mmol/g or less; 1.4 mmol/g or less; 1.3 mmol/g or less.

The present lignin derivatives may comprise other alkoxy groups apartfrom ethoxy groups such as C₁-C₆ alkoxy groups; C₁-C₄ alkoxy groups;C₁-C₃ alkoxy groups; methoxy and/or propoxy.

Quantification of the alkoxy groups can be performed using highresolution ¹³C NMR spectroscopy. For example, quantification of ethoxylgroups can be performed by high resolution ¹³C NMR spectroscopy.Identification of ethoxyl groups can be confirmed by 2D NMR HSQCspectroscopy. 2D NMR spectra may be recorded by a Bruker 700 MHzUltraShield Plus standard bore magnet spectrometer equipped with asensitive cryogenically cooled 5mm TCI gradient probe with inversegeometry. The acquisition parameters are the following: standard Brukerpulse program hsqcetgp, temperature of 298 K, a 90° pulse, 1.1 sec pulsedelay (dl), and acquisition time of 60 msec.

Quantification of ethoxyl groups was performed using quantitative ¹³CNMR spectroscopy. Identification of ethoxyl groups was confirmed by 2DNMR HSQC spectroscopy. 2D NMR spectra were recorded by a Bruker 700 MHzUltraShield Plus standard bore magnet spectrometer equipped with asensitive cryogenically cooled 5mm TCI gradient probe with inversegeometry. The acquisition parameters were as follow: standard Brukerpulse program hsqcetgp, temperature of 298 K, a 90° pulse, 1.1 sec pulsedelay (dl), and acquisition time of 60 msec.

The derivatives of native lignin herein may be incorporated into resincompositions as epoxy resins, urea-formaldehyde resins,phenol-formaldehyde resins, polyimides, isocyanate resins, and the like.The lignin derivatives herein are particularly useful in phenolicresins.

Phenol-formaldehyde resins can be produced by reacting a molar excess ofphenol with formaldehyde in the presence of an acid catalyst, such assulfuric acid, hydrochloric acid or, oxalic acid (usually in an amountof 0.2 to 2% by weight based on the phenol) or a basic catalyst such assodium hydroxide. To prepare the so-called “high ortho” novolac resins,the strong acid catalyst is typically replaced by a divalent metal oxide(e.g. MgO and ZnO) or an organic acid salt of a divalent metal (e.g.zinc acetate or magnesium acetate) catalyst system. The resinsso-produced are thermoplastic, i.e., they are not self-crosslinkable.Such novolac resins are converted to cured resins by, for example,reacting them under heat with a crosslinking agent, such as hexamine(also called hexa or hexamethylenetetramine), or for example, by mixingthem with a solid acid catalyst and paraformaldehyde and reacting themunder heat. Novolac resins also may be cured with other cross linkerssuch as resoles and epoxies. The lignin derivative may be mixed withphenol at any suitable ratio. For example, a lignin:phenol weight ratioof about 1:10 to about 10:1, about 1:8 to about 8:1, about 1:6 to about6:1, about 1:5 to about 5:1, about 1:4 to about 4:1, about 1:3 to about3:1, about 1:2 to about 2:1, about 1:1. The lignin derivative maycomprise any suitable amount of the total resin composition. Forexample, from about 1%, by weight, or greater, about 0.5% or greater,about 10% or greater, about 20% or greater, about 30% or greater, about35% or greater, about 40% or greater, of the total resin composition.The lignin derivative may comprise from about 80%, by weight, or less,about 60% or less, about 50% or less, of the total resin composition.The resin compositions may comprise a variety of other optionalingredients such as adhesion promoters; biocides (e.g. bactericides,fungicides, and moldicides), anti-fogging agents; anti-static agents;bonding, blowing and foaming agents;

dispersants; fillers and extenders; fire and flame retardants and smokesuppressants; impact modifiers; initiators; lubricants; micas; pigments,colorants and dyes; plasticizers; processing aids; release agents;silanes, titanates and zirconates; slip and anti-blocking agents;stabilizers; stearates; ultraviolet light absorbers; foaming agents;defoamers; hardeners; odorants; deodorants; antifouling agents;viscosity regulators; waxes; and combinations thereof.

The present disclosure provides binder compositions comprising anysuitable amount of MDI and any suitable amount of lignin derivative. Forexample, the binder compositions may comprise about 0.1% to about 25%,about 1% to about 15%, about 3% to about 10%, of lignin derivative byweight of the total binder composition.

The present disclosure provides a method of incorporating derivatives ofnative lignin in compositions comprising MDI. In particular, the methodcomprises:

-   -   a) providing a composition comprising derivatives of native        lignin in a suitable solvent;    -   b) providing a resin composition comprising MDI;    -   c) mixing the compositions; and    -   d) removing the solvent.

The present method provides for the modification of a MDI adhesive resin(usually a liquid) with an extracted lignin (usually a solid, driedbefore use) to form a relatively stable liquid MDI—lignin adhesiveresin. The lignin may be dissolved in a suitable solvent such asacetone. The resulting solution may then be mixed with liquid MDI resinsat a predetermined ratio. The solvent may then be extracted by, forexample, vacuum distillation at low temperatures. During thedistillation, MDI reacts with the lignin to form a relatively homogenousand stable MDI-lignin resin system. The solvent may be recovered andreused.

The present compositions may be incorporated into any suitablefibreboard or similar material. For example, low density fibreboard(LDF), medium density fibreboard (MDF), high density fibreboard (HDF),strawboard & other agricultural fibre/particle boards, oriented strandboard (OSB), particle board, termite-resistant OSB made with a pMDIresin and borate compounds, termite-resistant MDF made with a pMDI resinand borate compounds, wood fibre insulation board (WFIB), polyurethanefoams, and the like. The present compositions have be useful in foundryresins. The present disclosure provides a method for producing afibreboard comprising:

-   -   a) providing fibres to a blowline;    -   b) providing a binder comprising polymeric MDI and a derivative        of native lignin;    -   c) treating the fibres with the binder;    -   d) preferably at least partially drying the treated fibres; and    -   e) pressing the treated fibres to form a fibreboard.

Fibreboard is typically manufactured via a multi-step process. Woodchips, or other suitable materials, are fed into a digester where theyare exposed to steam and/or high pressures in order to soften them. Thetreated material is then fed into a refiner where mechanical forcesseparate the component fibres. The fibres exit the refiner via a“blowline” where they are transported in steam. Typically, binders areadded to the fibres in the blowline. The hot, moist conditions in theblowline are such that the isocyanates rapidly react with the water toform polyureas—that is, they “precure”.

Typically the blowline deposits the treated fibres in a dryer, and theninto pressing devices which produce the panels. Ideally, polymerizationof the binder into its final thermoset form would take place in thepress, not prior to pressing the fibreboard into its final form.However, because isocyanates are so reactive it is likely that asignificant amount of isocyanate is converted to polyurea prior topressing. This can lead to the formation of solids, which foul theblowline or the dryer. Also, pre-polymerization renders a significantportion of the binder inactive, reducing bonding efficiency.Furthermore, pre-cure can lead to structuring of the surface of thepanel before pressing. This can lead to “crashing” of the surface duringpressing and to a correspondingly lower performance characteristics suchas MOR and MOE.

The preferred fibreboard products are manufactured from wood fibres,although other cellulosic fibres may also be used, including thosemanufactured from agricultural products.

The present disclosure provides a method of forming fibreboard, andparticularly medium density fibreboard. Processes for production ofmedium density fibreboard are well known and a process is described,generally, below.

In producing medium density fibreboard, a polyisocyanate resin isapplied directly to the hot and wet fibre material in the blowline outof the refiner of a fibreboard manufacturing plant. Generally, thematerial is first screened to remove oversized and undersized material,e.g., fines and dirt. The material may also be subjected to a washingstep.

The material is conveyed to storage bins that feed pressurizeddigester-refiner systems. The refiners refine the raw material intofibre under steam pressure. The material passes from thesteam-pressurized digester into the refining section while still underpressure, and this pressure is maintained during the refining. Adigester is provided for pre-steaming of the raw material.Advantageously, molten wax is added to the material as they are fed tothe digester. Generally, the material is steamed in the digester forabout five to ten minutes at a pressure of about 550 kPa to 830 kPa.

As the material emerges from the digester, it passes through a refiner,which is also operated under steam pressure. The material is shreddedinto fibres in the refiner and then blown through an orifice (i.e., theblow-valve) out of the refiner into the “blowline”. Typically, the steampressure in the refiner can be from about 550 kPa to 1030 kPa, withtemperatures ranging from about 140° C. to 205° C. The fibres whichemerge from the refiner into the blowline generally have a moisturecontent of 50% or higher, by weight, based on the total solids weight,and a temperature of at least about 100° C. to 204° C. (usually aboveabout 118° C.).

The present compositions may be introduced into the blowline to treatthe hot fibre. For example the binder may be added to the material as itemerges from the refiner.

After refining, the material is conveyed through the blowline into aflash tube dryer, where the fibre moisture content is reduced to about2% to 20%, by weight. Typically, the treated fibre is in an air streamtube dryer for about 30 seconds, during which time it is at atemperature of about 38° C. to 260° C.

After refining, treating with the binder, and drying, the fibre and airare separated via a separator air cyclone. Next, the fibre istransported to mechanical formers that uniformly lay down the fibre onto a moving ‘forming line’.

The material can be treated in a pre-compressor to make it easier tohandle. After pre-compression, the material is cut into desired lengthsand fed into a conventional board-forming press, such as a typicalmedium density fibreboard press having multiple steam or oil heatedplatens, or a continuous press which consolidates the material betweentwo opposing steel belts. The press consolidates and compresses thematerial to the desired thickness while the heat cures the bindercomposition. Typically, during the pressing operation the material isgenerally heated to a temperature of about 121° C. to 232° C. andcompressed at about 690 kPa to 6900 kPa of pressure. Pressing times aretypically about 2 to 10 minutes.

The compositions of the present disclosure may be added to the fibrematerial at any suitable quantity. For example, from about 0.5% to about25%, from about 1% to about 15%, from about 2% to about 10%, from about3% to about 8%, by weight based on the dry weight of the fibre material.

MDF produced according to the present disclosure has a good modulus ofrupture (MOR) and modulus of elasticity (MOE) as well as an acceptableinternal bond (IB) strength.

EXAMPLES Example 1

MDI/Lignin Production

Two batches of 10 g of powdered lignin derivative are dissolved in twoaliquots of 50 g of acetone to form 20% wt./wt. solutions. 100 g of MDI(Rubinate 1780) is then mixed into one solution and 200 g of MDI(Rubinate 1780) is mixed into the other. The solutions are thensubjected to vacuum distillation at room temperature for 2 hours. Thisremoves 95% of the acetone which can be stored and re-used. The twocompositions are stored and their viscosities measured over a period ofseveral days (Table 1). The results indicate that the mixtures are notentirely stable but are not so unstable as to be unusable.

TABLE 1 The viscosity and stability of the MDI-lignin resins Viscosity(mPa · s) Storage time 5% lignin mix 10% lignin mix 0 600 1600 24 h 7803600  6 days 880 9300 10 days — 11250  17 days 1350  —

In addition, 5 g and 10 g of hardwood lignin powder are directly mixedwith 100 g of MDI resin (Rubinate 1780). The suspensions appear stablefor at least 24 hours, but separation or precipitation occurs over anextended period of time.

A sample of the 5% MDI-lignin mixture manufactured using acetone, andone sample each from the 5% and 10% MDI-lignin compositions made viadirect mixing, were used to manufacture a medium density fibreboard(MDF) using a standard blowline. The three resultant boards weremeasured for their shear strength (Table 2) according to the ABES method(Wescott, J. M., Birkeland, M. J., Traska, A. E., New Method for RapidTesting of Bond Strength for Wood Adhesives, Heartland ResourceTechnologies Waunakee, Wis., U.S.A. and Frihart, C. R. and Dally, B. N.,USDA Forest Service, Forest Products Laboratory, Madison, Wis., U.S.A.,Proceedings 30^(th) Annual Meeting of The Adhesion Society, Inc., Feb.18-21, 2007, Tampa Bay, Fla., USA).

TABLE 2 Shear strength of the mixes (yellow birch veneer, thickness:1.56 mm) Strength (MPa) Resin mix 150° C., 90 s 200° C., 90 s 5% lignin(acetone 3.3 (1.2) 5.4 (0.7) solution) mixed MDI 5% lignin directlymixed 4.0 (0.6) 5.8 (0.8) with MDI 10% lignin directly 4.3 (1.1) 7.0(1.9) mixed with MDI

Further MDI-bonded MDF panels were made at pilot scale. Wood fiber,which was dry and unresinated, was sourced from a Canadian MDF mill. Ina fiberboard pilot plant, a weighted amount of the wood fiber wasblended with a predetermined amount of pMDI resin or lignin-modifiedpMDI resin and a predetermined amount of emulsion wax in anair-suspension tube blender. Using the resulting resinated wood fiber, ahomogenous fiber mat was constructed in a 710 mm×710 mm forming box withTelflon sheets on top and bottom of the mat, which was then hot pressedinto a MDF panel by a Dieffenbacker press (864 mm×864 mm) equipped witha PressMan monitoring system.

Wood species: SPF

Fiber type: mechanically refined with a moisture content of about 8.5%

Control resin: RUBINATE 1780 (pMDI) at 4% add-on rate (dry wood basis)

Experimental resin: lignin—MDI containing 5% lignin at 4% add-on rate(dry wood basis)

Wax: emulsion wax (58% solids) at 0.5% add-on rate (dry wood basis)

Moisture content of blended fiber: 6.5%-7.5%

Target panel density: 768 kg/cu. m

Target panel thickness: 9.5 mm

Press temperature: 182 C (360 F)

Press time: 280 seconds

Pressing method: Press fast closed to 15% above target panel thicknessand then slow closed to target thickness over 60 seconds, following byholding and degassing.

The resulting MDF panels were conditioned under ambient conditions for 7days, and then tested for vertical density profile, average density,modulus of elasticity, modulus of rupture, internal bond strength, andthickness swell and water absorption after 24-hour water soak andcompared to MDF made with MDI alone, and to the American NationalStandard Institute ANSI STD A208.2-2003 (Table 3).

TABLE 3 Press Press Resin Temp Time D Type Resin % (° F.) (sec.)(lb/ft³) IB (psi) IB/D MOR (psi) MOE (Mpsi) WA (%) TS (%) MDI 4.0 360280 48.6 204.3 ± 24.3 4.20 5,135 ± 437 0.468 ± 0.023 24.5 ± 1.8 15.0 ±1.6 MDI- 4.0 360 280 48.6 161.0 ± 23.5 3.31 5,731 ± 434 0.528 ± 0.03824.7 ± 2.2 17.4 ± 0.9 Lignin American N/A N/A N/A N/A 44-152 N/A 3,5000.350 N/A N/A ANSI STD A208.2 (2003)

Example 2

Further testing was performed to compare OSB panel performance for alignin-phenol-formaldehyde resin (LPF) and a commercialphenol-formaldehyde (PF) resin as adhesives for

OSB face layers and to evaluate the feasibility of replacing commercialpMDI resin in OSB core layers with 30%, 40% and 50% LPF resins.

OSB Panel Manufacturing:

Face Core Resin solids pMDI solids Lignin-PF add-on rate add-on ratesolids add-on Group No. Resin type (%) (%) rate (%) 1 Commercial PF 3.002.00 0 2 Lignin-PF 3.00 2.00 0 3 Commercial PF 3.00 1.40 0.90 4Commercial PF 3.00 1.20 1.20 5 Commercial PF 3.00 1.00 1.50

Wood species: Aspen

OSB strands: screened and dried to 2% moisture content.

Target mat moisture: 6%-7%

Face/core ratio: 50/50

Panel thickness: 7/16″

Panel dimension: 4′×8′× 7/16″

Target density: 38 lb/ft³

Face resin: PF or Ligin-PF at 3% solids add-on (warmed to 30° C. beforeblending)

Core resin: pMDI/lignin-PF (100:0, 70:30×1.5, 60:40×1.5 and 50:50×1.5)

E-wax: EW58S at 1% solids add-on (58% solids diluted with water to 50%solids)

Press temperature: 215° C.

Press cycle time: 155 seconds

Hot stacking: Yes

Replicates: 4 for each group

Total number of panels produced: 20

Panel Test Results:

Concentrated static load 4-point tests according to the American PS-2standard

Group 1 2 3 4 5 Surface Commercial Lignin- Commercial CommercialCommercial PF PF PF PF PF Resin Loading 3.00% 3.00% 3.00% 3.00% 3.00%Core pMDI- pMDI- Lignin*- Lignin*- Lignin*- R1840 R1840 PF PF PF pMDI-pMDI- pMDI- R1840 R1840 R1840 Resin Loading 0.90% 1.20% 1.50% 2.00%2.00% 1.40% 1.20% 1.00% Density @ test 39.0 39.3 39.3 39.2 39.4 point(10″ × 10″) std 1.28 1.28 2.04 1.44 2.67 Thickness (inch) 0.43 0.4340.44 0.44 0.43 std 0.01 0.01 0.01 0.01 0.01 Deflection (inch) 0.38 0.3940.38 0.37 0.38 std 0.03 0.02 0.03 0.03 0.04 Ultimate Load (lbf) 444 386432 433 402 std 38.1 36.8 59.1 46.6 44.6 fail/pass 1/15 12/4 4/12 4/127/9 APA PRP-108 (2001) Performance Criteria: Minimum Ultimate 400 lbfLoad - Maximum Deflection @ 200 lbf 0.500 in *HPL ™ lignin (availablefrom Lignol Innovations, Burnaby, Canada, V5G 3L1)

The average density, vertical density profile, internal bond strength(TB), modulus of rupture (MOR), modulus of elasticity (MOE), andthickness swelling (TS) and water absorption (WA) was measured after24-hour water soak.

MOR MOE (par- (par- IB/ TS allel) allel) IB Core- Density (edge) WAGroup (psi) (Mpsi) (psi) density (lb/ft³) (%) (%) 1 4320 0.861 37.4 0.5237.7 26.0 49.2 2 3574 0.801 27.7 0.37 38.6 37.9 62.9 3 4164 0.878 35.70.48 38.7 27.7 48.9 4 4539 0.905 28.1 0.40 37.8 27.7 51.6 5 4276 0.90825.3 0.36 39.3 28.8 54.5

The above results demonstrate that it is feasible to use LPF resin at40% phenol replacement and that pMDI is an excellent cross-linker forLPF.

What is claimed is:
 1. An adhesive system comprising: a. a resincomprising at least about 30% by weight of phenol-formaldehyde resin andat least about 30% by weight of derivative of native lignin; and b. anisocyanate-based binder.
 2. A composition according to claim 1 whereinthe composition comprises at least about 35% by weight of derivative ofnative lignin.
 3. A composition according to claim 1 wherein thederivative of native lignin has an ethoxy content of 0.45 mmol/g orgreater.
 4. A composition according to claim 1 wherein theisocyanate-based binder comprises methylene diphenyl diisocyanate.
 5. Acomposition according to claim 1 wherein the isocyanate-based bindercomprises methylene diphenyl diisocyanate and a derivative of nativelignin.
 6. A composition according to claim 1 wherein theisocyanate-based binder comprises methylene diphenyl diisocyanate and aderivative of native lignin wherein the derivative of native lignin hasan aliphatic hydroxyl content of from about 0.6 mmol/g to about 6.5mmol/g.
 7. Use of the system according to claim 1 for the production ofa fibreboard.
 8. Use of the system according to claim 1 as an adhesivefor low density fibreboard (LDF), medium density fibreboard (MDF), highdensity fibreboard (HDF), strawboard & other agricultural fibre/particleboards, oriented strand board (OSB), particle board, wood fibreinsulation board (WFIB), or polyurethane foams.
 9. A method of producinga fibreboard a) providing fibres to a blowline; b) providing an adhesivesystem according to claim 1; c) treating the fibres with the adhesive;d) preferably at least partially drying the treated fibres; and e)pressing the treated fibres to form a fibreboard.
 10. A bindercomposition comprising methylene diphenyl diisocyanate and a derivativeof native lignin.
 11. A composition according to claim 10 wherein thederivative of native lignin has an aliphatic hydroxyl content of fromabout 0.1 mmol/g to about 8 mmol/g.
 12. A composition according to claim10 wherein the derivative of native lignin has an aliphatic hydroxylcontent of from about 0.6 mmol/g to about 6.5 mmol/g
 13. A compositionaccording to claim 10 comprising from about 0.1% to about 25%, byweight, of the derivative of native lignin.
 14. A composition accordingto claim 10 comprising from about 50% to about 99%, by weight, ofmethylene diphenyl diisocyanate.
 15. A method of producing a compositionaccording to claim 10, said method comprising: a) providing acomposition comprising derivatives of native lignin in a suitablesolvent; b) providing a resin composition comprising methylene diphenyldiisocyanate; c) mixing the compositions; and d) removing the solvent.16. A fibreboard comprising a composition according to claim
 10. 17. Useof a composition according to claim 10 as a binder for low densityfibreboard (LDF), medium density fibreboard (MDF), high densityfibreboard (HDF), strawboard & other agricultural fibre/particle boards,oriented strand board (OSB), particle board, wood fibre insulation board(WFIB), or polyurethane foams.
 18. A method of producing a fibreboard f)providing fibres to a blowline; g) providing a binder comprisingmethylene diphenyl diisocyanate and a derivative of native lignin; h)treating the fibres with the binder; i) preferably at least partiallydrying the treated fibres; and j) pressing the treated fibres to form afibreboard.